Dense samples of nominal composition Er1.96Ca0.04Ti2O6.98 were prepared by

conventional ceramic synthesis to evaluate the ionic conductivity. The electrical

properties were studied by impedance spectroscopy under oxidizing conditions as a

function of pO2, pH2O and pD2O at 360 to 600C. The microstructure was investigated

by analytical transmission electron microscopy before and after the impedance

study. In both cases the grain boundaries contained an amorphous phase; enriched

in Si and Ca. Three different contributions to the sample impedance, with different

time constants, were identified, one assigned to the grain interior and two to grain

boundaries. For the grain interior, oxygen vacancies were found to be the major

charge carrier. In contrast, protons were found to play an important role as charge

carriers in the grain boundary related processes. The ionic transport over grain

boundaries in Er1.96Ca0.04Ti2O6.98 was discussed in terms of effects of additional

phases in the grain boundaries and space charge layers.

Proton and Oxide Ion Conductivity in Grain Boundaries and Grain Interior of Ca-

Doped Er2Ti2O7 with Si-Impurities. H.Fjeld, R.Haugsrud, A.E.Gunnæs, T.Norby:

Solid State Ionics, 2008, 179[33-34], 1849-53